Protein composes 10-30% of cell mass and is the basic structural material of the body. however, not all proteins are construction materials. many play vital roles in cell function. proteins, which include enzymes (biological catalysts), hemoglobin of the blood, and contractile proteins of muscle, have the most varied function of any molecules in the body. all proteins contain carbon, oxygen, hydrogen, and nitrogen, and many contain sulfur as well. the building blocks of proteins are

(me out over the last several centuries, scientists have made the following broad observations while investigating several branches of the life sciences: -the fossil record shows that different types of organisms have existed at different times in earth's history. -many organisms have similar body structures that seem to be adapted to different ways of living in their environment. -organisms of different species often share similarities in stages of embryonic development. -many species share genetic similarities, and almost all organisms use the same basic building blocks to construct proteins. -often, the extent of two species' similarities can be predicted from their geographic closeness to each other. -a great deal of change has been observed among species that have experienced strong selective pressures through many generations. scientists have carefully considered and rigorously tested the observations listed above. when scientists offer a of these observations, they are making 1.) testable explanation, deductive explanation 2.) scientific interference, scientific law